Imiquimod is a topical immune response modifier and a 5% formulation has been approved for the treatment of AKs in the US as a 2x/week for 16 week regimen and in Europe as a 3x/week for 4 week regimen for 1 or 2 courses of therapy. Topical imiquimod treatment may also reduce subclinical lesions in the treatment area, resulting in fewer "new" AK lesions developing over the same period of time when compared to focal treatment. In a comparison of cryosurgery versus imiquimod for the treatment of AKs, Krawtchenko et al reported initial complete clearance rates of 68 and 85% by clinical assessment, respectively. However, the treatment field sustained clearance rate was 4% versus 73%, respectively. Tan et al reported that while application of imiquimod or vehicle following cryosurgery resulted in comparable target AK clearance rates at 12 weeks of 79% versus 76%, respectively, the imiquimod group had fewer total AKs and fewer subclinical AKs.